The best question has many answers. I am reminded of the story about a student who protested when his answer was marked wrong on a physics test.

In answer to the question, "How could you measure the height of a tall building, using a barometer?" he was expected to explain that the barometric pressures at the top and the bottom of the building are different, and by calculating, he could determine the building's height. Instead, he answered, "I would tie the barometer to a string, lower it to the ground and measure the length of the string."

His instructor admitted that the answer was technically correct but did not demonstrate a knowledge of physics.

The student then rattled off a whole series of answers involving physics — but not one using the principle in question: He would drop the barometer and time its fall. He would make a pendulum and time its frequency at the top and the bottom of the building. He would walk down the stairs marking "barometer units" on the wall.

When the instructor finally demanded the "simplest" answer to the question, the student replied, "I would go to the building superintendent and offer him a brand-new barometer if he will tell me the height of the building!"